Replace balance - but do not know the brand of window

I apologize, first, since I may not use the correct terms/words.

I am selling this home, and need to fix window. It is a vinyl, single hung, tilt window. The balance bar there is not covered by a plastic piece, it seems to be held in place by the white clip on the side of the window. I did see 28 E on the metal balance that is currently in the window. It seems there is a separate locking mechanism, or pivot locking shoe? My handyman was able to pull the string and rehook it on the left side of the window, but the right side, we can not release the tension on the string, and did not want to force it. I have been to Home Depot, Lowe's and a local lumber and window dealer. They can not help me unless I know what brand of window this is - I can tell you it is not an Anderson, Jeld-Wen, or Relibilt window, I have spent a good bit of time of help line calls. I have learned more about windows than I care to tell you. Also, the glass in the window is made by Guardian Glass, Galax, VA the numbers etched in the glass are z97.1 1-2004, cfr 1201-11 97. I live at thee beach, so it is "hurricane" grade glass.

Thx - Leslie